1. Field of the Invention
This invention relates in general to certain new and useful improvements in digitizing scanning apparatus, and more particularly, to an improved digitizing scanning apparatus which provides a unique drive mechanism and which also permits prescanning for calibration compensating for non-linearities in light distribution from a light source.
2. Brief Description of the Prior Art
In recent years, there has been an increased interest in digital scanning apparatus for purposes of document control and document storage. Most digital scanners utilize movement of a scanning element with respect to a plate on which an image to be copied is located. Relative movement exists between the plate which holds the image and the scanning element. Electrical signals generated by the scanning element are then stored in a computer storage for re-generation of the original image.
Electronic digitizing scanners are still in their relative infancy in the electronics industry and the presently available digitalizing scanners are somewhat rudimentary and overly complex in their construction and in their operation.
In one prior art digitizing scanning apparatus, a document was moved through a scanning path by means of a drive mechanism which relied upon drive rollers and cooperating idler rollers. However, the idler rollers and the drive rollers were fixed in position relative to one another in order the create a gap approximately the size of the thickness of the document being fed. There was no adjustability provided and therefore, if there was a thicker document, a greater amount of driving pressure was imposed upon the document. In like manner, if the document was thinner than the gap, there was insufficient pressure imposed upon the document to move the same at a proper speed through the scanning path.
Another one of the problems inherent in the prior art digitizing scanning apparatus is the fact that any calibration did not properly account for non-linearities in a light source. In co-pending U.S. Pat. application Ser. No. 094,398 filed Sept. 8, 1987, there is provided a digitizing scanning apparatus which utilizes an elongate tube source of light. In this case, the light was disposed transverse to the direction of movement of a document to be scanned thereby creating segments of a lighted area. In this way, successively lighted segments could be successively scanned.
In this prior art apparatus, attempts were made to compensate for any non-linearities in the light source. Thus, if there was a dark spot on the light source, an integration of the light across the transverse direction would attempt to compensate for and integrate light and dark areas. However, this integration did not account for the fact that light from a dark spot on the light source was also mixed with light from adjacent areas thereby partially cancelling out the effect of the dark spot. Thus, there was an over integration of the light to account for any dark spot and this resulted in light streaks on the image itself when reproduced.